(has no experience in pixelling whatsoever) but!I agree with missy's earlier comment about the black outline. just tweaking the outline color has made a big difference in the sprites I've seen over the years (via playing pokemon) and on deviantart. I think mixing more dark browns would also soften the image when it actually cross-stitched too and make it even more cute 'w'. Black stitching can look a bit harsh depending on how and where it's used so...

About the arms now, the one thats raised looks fine to me, but the lower one looks kind of noodle-like right now. It might use some more definition. I'm assuming her hand is curved inward with her palm facing towards her. To further emphasize that, what about adding another small shadow on her arm where her wrist is bent inward?

Well, I don't know how helpful this is, but what about being less strict with the black outline? Using different shades of brown might help with the foreshortening effect along with the shading that you already used. If you intersperse lighter pixels at the base of an arm, maybe one at the end of a string of three, and then have all of the pixels in the lighter shade that you chose by the lightest point in the limb, I think that it works effectively as a type of shading. Fighting games do this a lot, but I think one of the most effective examples is in the DS Pokemon games- [link] It's used really well for the girl in the orange shorts on the edge of the second row, though kicking the screen is a bit more extreme than doing ballet.

Anyway, I hope that's helpful! I'm not sure if that's what's being perceived as off, and it's really quite a cute sprite! Her hair looks great, and the expression fits the character well!